Oscillation generator system



1945- v M. MORRISON 2,390,659

OSCILLATION GENERATOR SYSTEM Original Filed March 17, 1937' very low value.

Patented Dec. 11, 1945 OSCILLATION GENERATOR SYSTEM Montford Morrison, Upper Montclair, N. J.

Substituted for abandoned application Serial No. 131,286, March 17, 1937. This application July 24, 1943. Serial No. 496,093.

3 Claims.

This invention relates to new and useful improvements in oscillation generator systems and means for controlling same, and particularly to systems which may be either self-excited or excited by an independent means without modification in the generator system proper.

This application is a substitute for a prior application,.Serial No. 131,286, filed March 17, 1937.

Among the objects of my invention are to produce an oscillation system in which the ratio of the output energy to the control energy is a high value; to produce an oscillation system having a high degree of stabilization under self-excitation and at the same time one which is easily, and which may be definitely, controlled by an external source of periodic current; and to provide an arrangement in which the relative phase angle between the output wave and control current may be easily adjusted. Other and further objects will appear from the specification and the claims.

The invention will be more fully understood from the following description if read in connection with the accompanying drawing,

Fig. 1 of which is a circuit diagram of an arrangement embodying the principles of the invention when self-excited;

2 is a circuit diagram of an' arrangement embodying the invention. when external excitation. is used.

Referring to Fig- 1, l is a source of direct'current, 2 is a condenser shunted across said source, 3, 4 and 5 are series inductors cooperating with capacitors 6, I and 8 forming a low-pass filter between the direct current source I and the terminals of the capacitor 8'. The terminal 9- of capacitor 8 is also the end terminal of the three inductors 3, 4 and 5, and the terminal H) of capacitor '8 is also the negative terminal of the three filter capacitors -6, l and 8, the negative terminal of capacitor 2 and the negative terminal of the direct current source I.

II is the closed circuit of the oscillator proper having, a capacitor l2, an inductor l3 and a transformer I4 loaded by translating device [5 tor withdrawing alternating current from the cal voltage is applied between two of the. electrodes, for instance, I! and IS, the resistance between the terminals l! and I58 breaks down to a The particular structure of the device is of no'iimportance. In the embodiment shown in Fig. I the device" I5 is illustrated as a discharge tube having a filament ll, a control grid 19 and a plate ll in a suitable gaseous ate mosphere to give the critical breakdown characteristic above specified. Tubes of this character and containing mercury vapor are known as grid glow" tubes and thyratrons, and tubes with three simple cylindrical electrodes are sometimes called trigger tubes.

In the plate circuit of the critical break-down device I6 an inductor 20 is connected to the oscillatory circuit II at terminal 2|. Terminal It is connected to the center of a filament transformer 22 which supplies filament energy for the tube I6. 23 is a source of voltage for biasing the grid [9 through variable resistor 24 and fixed resistor 25. The load l5 of transformer I4 is shun-ted by a circuit including a variable resistor 26 in series with a capacitor 21 shunted by a resistor 28. The variable resistor 26 is' shunted by a rectifying device 29 in series with the variable resistor 24.

Certain elements of Fig. 2 which are identical with those of Fig. 1 have the same numbers, the circuits of the two figures being identical with the exception of the grid control circuit which will now be described. The grid bias potential source 23 is connected through the secondary 30 of a transformer 3| to the fixed resistor 25. The characteristics of transformer 31 depend upon the frequencies involved, the only requirement being that the voltage wave form which is impressed upon the primary 32 be reasonably well transmitted to the secondary 30.

33 is a source of alternating current and 34' is a conventional bridge type full wave rectifier impressingupon the terminals 35 and 36 of resistor 31 a pure full wave rectified voltage. The resistor 31 and series capacitor 38' constitute a parallel f'eed' input for the transformer 3|.

The main oscillating circuit comprise ll, [2, l3, M, such equivalent resistance as transformer may possess, together with such other inherent resistance as may be found in the circuit.

In th illustrated embodiment large amounts of power may be withdrawn from the oscillating circuit-through the transformer. However, much more easily stabilized oscillation may be obtained byincreasing the Q of circuit II to a very high value, using this circuit as a master oscillator drivin a slave circuit as is commonly understood in the art.

It has been shown in Morecrofts Principles of. Radio Communication, third edition, page. 338, that in a closed oscillating circuit supplied by an orgy from a single direct current impulse, that the form of the wave train in this closed circuit resulting from said single impulse of excitation is affected by the duration of the impulse.

In accordance with the present invention, not the form of the wave train is the determining factor, but the quantity of energy in the impulse of excitation that is delivered to the circuit. This is limited by the fact that the impulse cannot have a duration beyond a certain value and is,

in fact, limited to one-half the duration of a cycle of the natural period of the oscillating circuit. In practicing the present invention the impulse circuit should not deliver a square top wave formbecause capacitors that must be usedin the oscillating circuit would by-pass high current values, whereby the grid-controlled valve device that I use would be called upon to operate beyond the capacity of the usual commercial device available for this purpose. I provide a low-pass filter in the input circuit of my oscillator to prevent the supplying of square top waves to the circuit which contains the capacitor. This low-pass filter, together with the other inductances and capaci tances in the circuit, will determine the period of time during which the open circuit will be closed and thus the impulsing period which, in accordance with the present invention, should never be more than one-half, but may be less than onehalf, the natural frequency of the normally closed oscillating circuit.

In accordance with my invention I provide means for supplying the energy lossper cycle in circuit II cyclically, such that the current proof the circuit vI I.

The device l6 has the further property of extinguishing its conductivity when the discharge current between its main electrodes approaches duced in circuit II is in fact an alternating current showing no detrimental decrement effects.

Referring to Fig. 2, the alternating voltage from generator 33 is rectified by full wave bridge circuit 34 and impressed upon terminals 35 and 36 of resistor 31, which with capacitor 38 form a parallel feed input circuit for transformer 3|. This will impress in the grid circuit of the critical breakdown device IS a full wave rectified alternating current. The device Iii has such characteristics that with a negative potential upon the grid I9 above a given critical value, no conduction current between electrodes I I and I 3 will cccur with normal plate voltage applied to the device. The'const'ant potential source 23 plus the added voltage of the secondary 30 is such that the minimum critical negative potential of the grid I9 is always exceeded except at the zero points of the rectifiedvoltage received from the secondary 30.

Unde these conditions the critical break-down device i6. is ignited or triggered off only at these zero points and under conditions of proper operating voltage between the electrodes I1 and [8.

Assuming that the grid potential of the critical breakdown device I6 is away from the said zero points, the device IE will not conduct current.

When the zero point is reached the resistance of tube l6 breaks down and current begins to flow from potential source I, the capacitor 2 being provided merelyto store energy so that the instahtaneous capacity of source I' may be small. The current flows through the filter circuit, the impulse energy dividing at the terminal 9, one part passing through the capacitor I2 and inductor 2H, and the remaining part passing through the inductor I3, transformer l4, combining with the other current through the inductor 29 and completing its circuit through the critical breakdown device I6 to terminal III of the power supply circuit;

The division of energy storage between the capacito I2 and the inductor I3 will depend upon zero, so that for a single ignition voltage upon the electrode I9, the duration of which does not exceed a small fraction of the period of oscillation in themain electrode circuit thereof, the conductivity of the device I6 will exist for only one lobe of the oscillation current. .The circuit II will, therefore, receive a unidirectional energy impulse for each momentary excitation of the control electrode I9 of device I6.

With afixed voltage at the source I, the char acteristics of the filter circuit in conjunction With the two coupled oscillator circuits provides for a definite measure of impulse energy suppliedper cycle to circuit II. With a properly predetermined wave form ofimpulse current of prope duration, the impulse energy periodically supplied to circuit II at thebeginning of each cycle will eliminate the decrement effect and circuit I I will oscillate as a continuous sine wave of current if the oscillator frequency of circuit I l is adjusted approximately to twice that of the alternating current generator 33 so that the critical breakdown device It receive two ignition points per cycle of the current from generator 33.

The natural frequency adjustment of circuit II is not critical and the current in circuit II will follow in phase and frequency within reasonable variations of these two quantities in alternating currentgenerator 33. The current in circuit II will flow cyclically, since the oscillations become forced whenever the frequency of the igniting circuit different from the natural period of the circuit. This is so because when the grid control circuit frequency is increased slightly, the losses are replaced in circuit II before they have been actually'dissipated, whereby more energy is supplied to the oscillating circuit than it can dissipate at its normal frequency. The

circuit must, therefore, operate faster to absorb infinitesimal grid currents; large amounts of oscillating currents may be obtained by this'invention with a reasonably small tube.

When it is desired to have the. oscillating circuit II self-excited, an exciting circuit of the characteristics shown in Fig. 1 may beemployed.

-While an oscillator can'be set into operation by one of more switchings in the circuit, its operation can be most easily understood by, considering the circuits already in operation.

The voltage across the resistor I5 during operation is sinusoidal and the current'through the variable resistor 24 is fixed mainly by the constants of the capacitor 21, its shunting resistor 28, rectifier 29, and the resistance value of 24, resistor 26 serving merely to by-pass certain undesirable currents. The current through resistor 24 is limited to unidirectional values by the rectifier 29. The value and the shape of the unidirectional current through resistor 24 is largely determined by the value of the capacitor 21 which is so fixed that in conjunction with the other elements of the circuit a steep Wave front of current is produced through the resistor 24 at the beginning of each cycle of the voltage at I5, and only at this point. At the beginning of each new cycle in the oscillation circuit, the critical break-down device I6 is ignited by means of grid l9 by a very steep wave front voltage, producing a system of self-excitation determined by the frequency of the oscillating circuit 1 I, the other factors being as before described.

Referring to Fig. 2, with a fixed voltage source I the only important variables in circuit H are the loading and temperature efiects, the temperature efiects being in reality a change of loading.

The frequency stability of such a circuit can be made of very high value by using-the above mentioned master oscillator and slave circuit and by employing temperature compensated resistance circuits or controlling the temperature of the circuits in which variation in resistance is a factor, as well as employing a critical break-down device for the element I6 which is not detrimentally subject to important variations.

The expression electron discharge means is used herein as a general term to designate all those means which are characterized by employing electron discharge as differentiated from mechanical contactors.

The expression closed metallic circuit in the claims is used to designate a circuit composed entirely of metallic conductors or their equivalent as distinguished from closed circuits which contain electron discharge tubes or their equivalents.

The herein described embodiments are merely given as practical cases, such circuits being capable of satisfactory operation with relatively large outputs of energy, but it will be obvious that the principles herein disclosed may be embodied in many other organizations widely different from those illustrated without departing from the spirit of the invention as defined in the claims.

What I claim is:

1. An oscillation generator system comprising a closed circuit having a given natural frequency, a normally open circuit coupled with said closed circuit and when closed having a higher natural frequency than the given natural frequency, a direct current source of electric power coupled with said open circuit, and means for closing said normally open circuit for an interval of time equal to one-half the natural period of the open circuit when closed, thereby impulsing the said closed circuit for the said one-half period of time.

2. An oscillation generator system comprising a closed circuit having a given natural frequency, a normally open circuit coupled with said closed circuit and when closed having a higher natural frequency than the given natural frequency, a direct current source of electric power coupled with the open circuit, and means for closing said normally open circuit for an interval of time equal to one-half the natural period of this circuit when closed, said interval of closing occurring periodically at a frequency substantially that of the given natural frequency, thereby impulsing the said closed circuit for the said one-half period of time.

3. An oscillation generator system comprising a closed circuit having a given natural frequency, a normally open circuit coupled with said closed circuit and when closed having a higher frequency than the given natural frequency, a direct current source of electric power coupled with said open circuit, and means for closing said normally open circuit for an interval of time equal to not more than one-half the natural period of the open circuit when closed, thereby impulsing said closed circuit for a period not more than one-half the period of its given natural frequency.

MONTFORD MORRISON. 

